1. Field of the Invention
The present invention relates to a semiconductor device including transistors that are called an insulated gate transistor, a MIS (metal insulator semiconductor) field effect transistor or an MOS transistor, and more particularly to a semiconductor device that can be suitably mounted on an ink jet printer used as an output terminal such as a copying machine, a facsimile machine, a word processor or a computer, or on a liquid jet apparatus for manufacturing a DNA chip or an organic TFT, a method of manufacturing the same, and a liquid jet apparatus.
2. Related Background Art
Now, an example of a semiconductor device used in the liquid jet apparatus will be described.
In a recording apparatus used as various output terminals, an electro-thermal converter, an element that switches the electro-thermal converter element (hereinafter referred to as xe2x80x9cswitching elementxe2x80x9d), and a circuit for driving the switching element are mounted on a common substrate as a recording head.
FIG. 19 is a schematic cross-sectional view showing a part of a recording head according to a conventional structure.
Reference numeral 901 denotes a semiconductor substrate made of single crystal silicon. Reference numeral 912 is a p-type well region, 908 is an n-type drain region having a high impurity concentration, 916 is an n-type field relaxation drain region having a low impurity concentration, 907 is an n-type source region having a high impurity concentration, and 914 is a gate electrode. These elements form a switching element 930 using a MIS field effect transistor. Reference numeral 917 denotes a regenerative layer and a silicon oxide layer that functions as an insulating layer, 918 is a tantalum nitride film that functions as a heat resistant layer, 919 is an aluminum alloy film that functions as a wiring, and 920 is a silicon nitride film that functions as a protective layer. These elements form a substrate 940 of the recording head. In this example, reference numeral 950 denotes a heating portion, and an ink is jetted from 960. Also, a roof 970 defines a liquid passage 980 in cooperation with the substrate 940.
Incidentally, improvements have been frequently made to the recording head and the switching element structured as described above. In recent years, demands have been further made to increase a drive speed, to save an energy, to increase integration, to reduce the costs and to enhance the performance, with respect to such products.
A plurality of MIS field effect transistors 930 used as the switching elements shown in FIG. 19 are produced within the semiconductor substrate 901. And these MIS field effect transistors 930 are operated independently or at the same time to drive the connected electro-thermal converter.
However, when the conventional MIS field effect transistor 930 functions under the condition where a large current required to drive a load such as the electro-thermal converter flows, a pn reverse bias junction portion between a drain and a well generates a leak current since it cannot withstand a high electric field, and therefore it cannot satisfy a breakdown voltage required as a switching element. In addition, when the on resistance of the MIS field effect transistor used as the switching element is large, there arises such a problem to be solved that a current necessary to drive the electro-thermal converter cannot be obtained by resulting wasteful current consumption.
The present invention has been made in view of the above circumstances, and therefore an object of the present invention is to provide a high-performance semiconductor device including an insulated gate transistor, which allows a large current to flow, and enables high-speed drive at a high breakdown voltage, energy saving and high integration.
Another object of the present invention is to provide a liquid jet apparatus which allows a large current to flow, and enables high-speed drive at a high breakdown voltage, energy saving and high integration.
Still another object of the present invention is to provide a method of manufacturing a high-performance semiconductor device which can achieve higher integration and reduced costs.
According to an aspect of the present invention, there is provided a semiconductor device in which a switching element for allowing a current to flow in a load and a circuit for driving the switching element are formed on a common substrate, characterized in that:
the switching element is a first insulated gate transistor which comprises:
a first semiconductor region of a second conductive type disposed at one main surface of a semiconductor substrate of a first conductive type;
a second semiconductor region of the first conductive type disposed within the first semiconductor region;
a first gate electrode disposed on a surface at which a pn junction between the second semiconductor region and the first semiconductor region terminates through an insulating film;
a first source region of the second conductive type disposed on one end portion side of the first gate electrode within the second semiconductor region; and
a first drain region of the second conductive type disposed within the first semiconductor region; and that
the circuit for driving the switching element comprises a second insulated gate transistor having a characteristic different from the first insulated gate transistor.
Here, the second insulated gate transistor preferably constitutes a level shift circuit that generates a drive voltage applied to the first gate electrode.
The drain region of the second insulated gate transistor preferably includes a low impurity concentration region.
It is preferable that the second insulated gate transistor constitute a level shift circuit that generates a drive voltage applied to the first gate, and that a low impurity concentration region be disposed within a drain region of the second insulated gate transistor.
The second insulated gate transistor preferably comprises a source follower transistor that constitutes a level shift circuit that generates a drive voltage applied to the first gate through a CMOS circuit.
A well potential of the second insulated gate transistor is preferably different from both a source potential and a drain potential.
A drain region of the second insulated gate transistor preferably has a low impurity concentration region that is formed to be shallower than the first semiconductor region.
A drain region of the second insulated gate transistor preferably has a low impurity concentration region having the same depth as that of the first semiconductor region.
The second semiconductor region is preferably formed to be deeper than the first semiconductor region.
A plurality of first insulated gate transistors are preferably arranged in an array, without dedicated element isolation regions being interposed therebetween.
The second insulated gate transistor is preferably an MOS transistor of the first conductive type which constitutes a low-voltage CMOS circuit.
It is preferable that the circuit for driving the switching element comprises a low-voltage CMOS circuit having the second insulated gate transistor, and a high-voltage CMOS circuit that is controlled by the low-voltage CMOS circuit, and that an MOS transistor of the first conductive type which constitutes the high-voltage CMOS circuit is a DMOS transistor produced in the same process as that for forming the first insulated gate transistor.
It is preferable that the semiconductor device of the present invention further comprise a level shift circuit that generates a drive voltage applied to the first gate electrode through the high-voltage CMOS circuit.
The second insulated gate transistor preferably includes source and drain regions of the first conductive type which are formed within the well of the second conductive type.
An electro-thermal converter that functions as the load is preferably connected to a drain of the switching element and is integrated.
The characteristic described above preferably refers to at least one selected from a threshold value, a breakdown voltage and a substrate current.
According to another aspect of the present invention, there is provided a semiconductor device in which a switching element for allowing a current to flow to a load and a circuit for driving the switching element are formed on a common substrate, characterized in that:
the switching element is formed of a DMOS transistor; and
the circuit for driving the switching element includes an MOS transistor having a characteristic different from that of the DMOS transistor.
Here, the MOS transistor is preferably of the same conductive type as that of the DMOS transistor.
A drain region of the MOS transistor preferably has a low impurity concentration region.
It is preferable that the MOS transistor constitute a level shift circuit that generates a drive voltage applied to a gate electrode of the DMOS transistor, and a low impurity concentration region be disposed within the drain region.
The MOS transistor is preferably a source follower transistor that constitutes a level shift circuit that generates a drive voltage applied to the gate electrode of the DMOS transistor through a CMOS circuit.
A well potential of the MOS transistor is preferably different from both a source potential and a drain potential.
A drain region of the MOS transistor preferably has a low impurity concentration region that is formed shallower than a base region that becomes a channel of the DMOS transistor.
A drain region of the MOS transistor preferably has a low impurity concentration region having the same depth as that of a base region that becomes a channel of the DMOS transistor.
A base region that becomes a channel of the DMOS transistor is preferably formed to be deeper than a lightly doped drain region.
A plurality of the DMOS transistors are preferably arranged in an array without dedicated element separation regions being interposed therebetween.
The MOS transistor preferably is an MOS transistor of the first conductive type which constitutes a low-voltage CMOS circuit.
It is preferable that the circuit for driving the switching element preferably comprises a low-voltage CMOS circuit having the MOS transistor and a high-voltage CMOS circuit that is controlled by the low-voltage CMOS circuit, and an MOS transistor of the first conductive type which constitutes the high-voltage CMOS circuit is a DMOS transistor produced in the same process as that for forming the DMOS transistor.
It is preferable that the semiconductor device of the present invention further comprise a level shift circuit that generates a drive voltage applied to the gate electrode of the DMOS transistor that functions as the switching element, through the high-voltage CMOS circuit.
The DMOS transistor preferably includes first conductive type source and drain regions formed within the second conductive type well.
An electro-thermal converter that functions as the load is preferably connected to a drain of the DMOS transistor for integration.
The DMOS transistor preferably comprises:
a first semiconductor region of a second conductive type disposed at one main surface of a semiconductor substrate of a first conductive type;
a second semiconductor region of the first conductive type disposed within the first semiconductor region;
a first gate electrode disposed on a surface in which a pn junction between the second semiconductor region and the first semiconductor region terminates, through an insulating film;
a first source region of the second conductive type which is disposed on one end portion side of the first gate electrode within the second semiconductor region; and
a first drain region of the second conductive type which is disposed within the first semiconductor region.
The second insulated gate transistor or an MOS transistor preferably has an on resistance that is equal or greater, and an operation breakdown voltage that is ⅔ or lower, as compared with those of the first insulated gate transistor or a DMOS transistor.
The second insulated gate transistor or an MOS transistor preferably has an on resistance that is equal or greater, and the maximum substrate current within an operation range which is 10 times or higher, as compared with those of the first insulated gate transistor or a DMOS transistor.
According to another aspect of the present invention, there is provided a liquid jet apparatus that jets a liquid by using a heat generated by an electro-thermal converter, characterized by comprising:
the above-mentioned semiconductor device;
a discharge opening disposed in correspondence with the electro-thermal converter that becomes a load;
a container that contains the liquid that is supplied onto the electro-thermal converter; and
a power circuit for supplying a power voltage to the semiconductor device.
According to still another aspect of the present invention, there is provided a method of manufacturing a semiconductor device in which a switching element and a circuit for driving the switching element are formed on a common substrate, characterized by comprising the steps of:
forming a first semiconductor region of a second conductive type on a surface of a first conductive type semiconductor substrate;
forming a gate insulating film on the first semiconductor region;
forming a first gate electrode on the surface of the first semiconductor region through the gate insulating film, and a second gate electrode on the surface of the semiconductor substrate through the gate insulating film;
forming a second semiconductor region of a first conductive type which is higher in concentration than the first semiconductor region, within the first semiconductor region by ion implantation of first conductive type impurities with the first gate electrode as a mask;
forming a lightly doped drain region of the second conductive type in the semiconductor substrate by ion implantation of second conductive type impurities with aid second gate electrode as a mask; and
forming a first source region of the second conductive type on a surface side of the second semiconductor region by ion implantation with the first gate electrode as a mask, forming a first source region of the second conductive type on a surface side of the first semiconductor region, forming a second source region of the second conductive type on a surface side of the semiconductor substrate by ion implantation, and forming a second drain region of the second conductive type so as to be apart from an end portion of the lightly doped drain region on the second gate electrode side.
In this example, the second semiconductor region may be formed so as to be higher in concentration than the first semiconductor region and deeper than the first semiconductor region, in order to electrically isolate the first semiconductor region by ion implantation of the first conductive impurities with the first gate electrode as a mask and by a heat treatment.
According to yet still another aspect of the present invention, there is provided a method of manufacturing a semiconductor device in which a switching element and a circuit for driving the switching element are formed on a common substrate, characterized by comprising the steps of:
forming a plurality of first semiconductor regions of a second conductive type on a surface of a semiconductor substrate of a first conductive type;
forming a gate insulating film on the plurality of first semiconductor regions;
forming a first gate electrode on a surface of one of the plurality of first semiconductor regions through the gate insulating film, and a second gate electrode on a surface in which a pn junction between the semiconductor substrate and another one of the plurality of first semiconductor regions terminates, through the gate insulating film;
forming a second semiconductor region of the first conductive type within one of the plurality of first semiconductor regions by ion implantation of first conductive type impurities, with the first gate electrode as a mask;
forming a first source region of the second conductive type by ion implantation of second conductive type impurities on the surface side of the second semiconductor region with the first gate electrode as a mask, forming a first drain region of the second conductive type on a surface side of the first semiconductor region, forming a second source region of the second conductive type on a surface side of the semiconductor substrate, and forming a second drain region of the second conductive type on the surface side of the first semiconductor region so as to be apart from a pn junction between the semiconductor substrate and the first semiconductor region.
In this example, the second semiconductor region may be formed so as to be higher in concentration than the first semiconductor region and deeper than the first semiconductor region, in order to isolate one of the plurality of first semiconductor regions.